From eec420a3759fe357afac3e795d946dc7f8f83503 Mon Sep 17 00:00:00 2001
From: Dave Mankoff <mankoff@google.com>
Date: Wed, 22 Sep 2021 10:21:17 -0400
Subject: [PATCH] Prevent NPE in NavigationBar

When the view detaches, we were left in a state where the view
was null but the a11y callbacks were still using it.

Test: atest SystemUITests
Fixes: 196285098
Change-Id: Ie53ac9d73c22be204d905079773f3f021010fd1d
---
 .../systemui/navigationbar/NavigationBar.java | 10 ++++++----
 .../navigationbar/NavigationBarTest.java      | 19 ++++++++++++++++++-
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/packages/SystemUI/src/com/android/systemui/navigationbar/NavigationBar.java b/packages/SystemUI/src/com/android/systemui/navigationbar/NavigationBar.java
index 43315f605099e..8576a280c5601 100644
--- a/packages/SystemUI/src/com/android/systemui/navigationbar/NavigationBar.java
+++ b/packages/SystemUI/src/com/android/systemui/navigationbar/NavigationBar.java
@@ -712,6 +712,7 @@ public class NavigationBar implements View.OnAttachStateChangeListener,
         mHandler.removeCallbacks(mAutoDim);
         mHandler.removeCallbacks(mOnVariableDurationHomeLongClick);
         mHandler.removeCallbacks(mEnableLayoutTransitions);
+        mNavigationBarA11yHelper.removeA11yEventListener(mAccessibilityListener);
         mFrame = null;
         mNavigationBarView = null;
         mOrientationHandle = null;
@@ -1391,10 +1392,11 @@ public class NavigationBar implements View.OnAttachStateChangeListener,
     void updateAccessibilityServicesState() {
         int a11yFlags = mNavigationBarA11yHelper.getA11yButtonState();
 
-        boolean clickable = (a11yFlags & SYSUI_STATE_A11Y_BUTTON_CLICKABLE) != 0;
-        boolean longClickable = (a11yFlags & SYSUI_STATE_A11Y_BUTTON_LONG_CLICKABLE) != 0;
-        mNavigationBarView.setAccessibilityButtonState(clickable, longClickable);
-
+        if (mNavigationBarView != null) {
+            boolean clickable = (a11yFlags & SYSUI_STATE_A11Y_BUTTON_CLICKABLE) != 0;
+            boolean longClickable = (a11yFlags & SYSUI_STATE_A11Y_BUTTON_LONG_CLICKABLE) != 0;
+            mNavigationBarView.setAccessibilityButtonState(clickable, longClickable);
+        }
         updateSystemUiStateFlags(a11yFlags);
     }
 
diff --git a/packages/SystemUI/tests/src/com/android/systemui/navigationbar/NavigationBarTest.java b/packages/SystemUI/tests/src/com/android/systemui/navigationbar/NavigationBarTest.java
index ed3c473aacf3a..36228dcb08c36 100644
--- a/packages/SystemUI/tests/src/com/android/systemui/navigationbar/NavigationBarTest.java
+++ b/packages/SystemUI/tests/src/com/android/systemui/navigationbar/NavigationBarTest.java
@@ -56,6 +56,7 @@ import android.testing.TestableLooper.RunWithLooper;
 import android.view.Display;
 import android.view.DisplayInfo;
 import android.view.MotionEvent;
+import android.view.View;
 import android.view.WindowManager;
 import android.view.WindowMetrics;
 import android.view.accessibility.AccessibilityManager;
@@ -122,6 +123,8 @@ public class NavigationBarTest extends SysuiTestCase {
     EdgeBackGestureHandler.Factory mEdgeBackGestureHandlerFactory;
     @Mock
     EdgeBackGestureHandler mEdgeBackGestureHandler;
+    @Mock
+    NavigationBarA11yHelper mNavigationBarA11yHelper;
 
     @Rule
     public final LeakCheckedTest.SysuiLeakCheck mLeakCheck = new LeakCheckedTest.SysuiLeakCheck();
@@ -256,6 +259,20 @@ public class NavigationBarTest extends SysuiTestCase {
         assertFalse((defaultNavBar.getNavigationIconHints() & NAVIGATION_HINT_IME_SHOWN) != 0);
     }
 
+    @Test
+    public void testA11yEventAfterDetach() {
+        View v = mNavigationBar.createView(null);
+        mNavigationBar.onViewAttachedToWindow(v);
+        verify(mNavigationBarA11yHelper).registerA11yEventListener(any(
+                NavigationBarA11yHelper.NavA11yEventListener.class));
+        mNavigationBar.onViewDetachedFromWindow(v);
+        verify(mNavigationBarA11yHelper).removeA11yEventListener(any(
+                NavigationBarA11yHelper.NavA11yEventListener.class));
+
+        // Should be safe even though the internal view is now null.
+        mNavigationBar.updateAccessibilityServicesState();
+    }
+
     private NavigationBar createNavBar(Context context) {
         DeviceProvisionedController deviceProvisionedController =
                 mock(DeviceProvisionedController.class);
@@ -287,7 +304,7 @@ public class NavigationBarTest extends SysuiTestCase {
                 mHandler,
                 mock(NavigationBarOverlayController.class),
                 mUiEventLogger,
-                mock(NavigationBarA11yHelper.class),
+                mNavigationBarA11yHelper,
                 mock(UserTracker.class)));
     }